"Targeting" nanoparticles: the constraints of physical laws and physical barriers

Recent advances in liposome-based targeted cancer therapy

Nano-drug delivery systems have opened new pathways for tumor treatment by overcoming some of the limitations of conventional drugs, such as physiological degradation, short half-life, and rapid release. Liposomes are promising nanocarrier systems due to their biocompatibility, low toxicity, and high inclusivity, as well as their enhanced drug bioavailability. Various strategies for active targeting of liposomal formulations have been investigated to achieve the highest drug efficacy. This review aims to summarize current developments in novel liposomal formulations, particularly ligand-targeted liposomes (such as folate, transferrin, hyaluronic acid, antibodies, aptamer, and peptide, etc.) used for the therapy of various cancers and provide an insight on the challenges and future of liposomes for scientists and pharmaceutical companies.

Metal nanoparticles as a potential technique for the diagnosis and treatment of gastrointestinal cancer: a comprehensive review

Gastrointestinal (GI) cancer is a major health problem worldwide, and current diagnostic and therapeutic approaches are often inadequate. Various metallic nanoparticles (MNPs) have been widely studied for several biomedical applications, including cancer. They may potentially overcome the challenges associated with conventional chemotherapy and significantly impact the overall survival of GI cancer patients. Functionalized MNPs with targeted ligands provide more efficient localization of tumor energy deposition, better solubility and stability, and specific targeting properties. In addition to enhanced therapeutic efficacy, MNPs are also a diagnostic tool for molecular imaging of malignant lesions, enabling non-invasive imaging or detection of tumor-specific or tumor-associated antigens. MNP-based therapeutic systems enable simultaneous stability and solubility of encapsulated drugs and regulate the delivery of therapeutic agents directly to tumor cells, which improves therapeutic efficacy and minimizes drug toxicity and leakage into normal cells. However, metal nanoparticles have been shown to have a cytotoxic effect on cells in vitro. This can be a concern when using metal nanoparticles for cancer treatment, as they may also kill healthy cells in addition to cancer cells. In this review, we provide an overview of the current state of the field, including preparation methods of MNPs, clinical applications, and advances in their use in targeted GI cancer therapy, as well as the advantages and limitations of using metal nanoparticles for the diagnosis and treatment of gastrointestinal cancer such as potential toxicity. We also discuss potential future directions and areas for further research, including the development of novel MNP-based approaches and the optimization of existing approaches.

Nanoparticles in Cancer Diagnosis and Treatment

The use of tailored medication delivery in cancer treatment has the potential to increase efficacy while decreasing unfavourable side effects. For researchers looking to improve clinical outcomes, chemotherapy for cancer continues to be the most challenging topic. Cancer is one of the worst illnesses despite the limits of current cancer therapies. New anticancer medications are therefore required to treat cancer. Nanotechnology has revolutionized medical research with new and improved materials for biomedical applications, with a particular focus on therapy and diagnostics. In cancer research, the application of metal nanoparticles as substitute chemotherapy drugs is growing. Metals exhibit inherent or surface-induced anticancer properties, making metallic nanoparticles extremely useful. The development of metal nanoparticles is proceeding rapidly and in many directions, offering alternative therapeutic strategies and improving outcomes for many cancer treatments. This review aimed to present the most commonly used nanoparticles for cancer applications.

Material design for oral insulin delivery

Frequent insulin injections remain the primary method for controlling the blood glucose level of individuals with diabetes mellitus but are associated with low compliance. Accordingly, oral administration has been identified as a highly desirable alternative due to its non-invasive nature. However, the harsh gastrointestinal environment and physical intestinal barriers pose significant challenges to achieving optimal pharmacological bioavailability of insulin. As a result, researchers have developed a range of materials to improve the efficiency of oral insulin delivery over the past few decades. In this review, we summarize the latest advances in material design that aim to enhance insulin protection, permeability, and glucose-responsive release. We also explore the opportunities and challenges of using these materials for oral insulin delivery.

Oral insulin delivery: Barriers, strategies, and formulation approaches: A comprehensive review

Diabetes Mellitus is characterized by a hyperglycemic condition which can either be caused by the destruction of the beta cells or by the resistance developed against insulin in the cells. Insulin is a peptide hormone that regulates the metabolism of carbohydrates, proteins, and fats. Type 1 Diabetes Mellitus needs the use of Insulin for efficient management. However invasive methods of administration may lead to reduced adherence by the patients. Hence there is a need for a non-invasive method of administration. Oral Insulin has several merits over the conventional method including patient compliance, and reduced cost, and it also mimics endogenous insulin and hence reaches the liver by the portal vein at a higher concentration and thereby showing improved efficiency. However oral Insulin must pass through several barriers in the gastrointestinal tract. Some strategies that could be utilized to bypass these barriers include the use of permeation enhancers, absorption enhancers, use of suitable polymers, use of suitable carriers, and other agents. Several formulation types have been explored for the oral delivery of Insulin like hydrogels, capsules, tablets, and patches which have been described briefly by the article. A lot of attempts have been made for developing oral insulin delivery however none of them have been commercialized due to numerous shortcomings. Currently, there are several formulations from the companies that are still in the clinical phase, the success or failure of some is yet to be seen in the future.

Shear stress regulation of nanoparticle uptake in vascular endothelial cells

Nanoparticles (NPs) hold tremendous targeting potential in cardiovascular disease and regenerative medicine, and exciting clinical applications are coming into light. Vascular endothelial cells (ECs) exposure to different magnitudes and patterns of shear stress (SS) generated by blood flow could engulf NPs in the blood. However, an unclear understanding of the role of SS on NP uptake is hindering the progress in improving the targeting of NP therapies. Here, the temporal and spatial distribution of SS in vascular ECs and the effect of different SS on NP uptake in ECs are highlighted. The mechanism of SS affecting NP uptake through regulating the cellular ROS level, endothelial glycocalyx and membrane fluidity is summarized, and the molecules containing clathrin and caveolin in the engulfment process are elucidated. SS targeting NPs are expected to overcome the current bottlenecks and change the field of targeting nanomedicine. This assessment on how SS affects the cell uptake of NPs and the marginalization of NPs in blood vessels could guide future research in cell biology and vascular targeting drugs.

An overview of in vitro 3D models of the blood-brain barrier as a tool to predict the in vivo permeability of nanomedicines

The blood-brain barrier (BBB) prevents efficient drug delivery to the central nervous system. As a result, brain diseases remain one of the greatest unmet medical needs. Understanding the tridimensional structure of the BBB helps gain insight into the pathology of the BBB and contributes to the development of novel therapies for brain diseases. Therefore, 3D models with an ever-growing sophisticated complexity are being developed to closely mimic the human neurovascular unit. Among these 3D models, hydrogel-, spheroid- and organoid-based static BBB models have been developed, and so have microfluidic-based BBB-on-a-chip models. The different 3D preclinical models of the BBB, both in health and disease, are here reviewed, from their development to their application for permeability testing of nanomedicines across the BBB, discussing the advantages and disadvantages of each model. The validation with data from in vivo preclinical data is also discussed in those cases where provided.

Nanoconstructs for theranostic application in cancer: Challenges and strategies to enhance the delivery

Nanoconstructs are made up of nanoparticles and ligands, which can deliver the loaded cargo at the desired site of action. Various nanoparticulate platforms have been utilized for the preparation of nanoconstructs, which may serve both diagnostic as well as therapeutic purposes. Nanoconstructs are mostly used to overcome the limitations of cancer therapies, such as toxicity, nonspecific distribution of the drug, and uncontrolled release rate. The strategies employed during the design of nanoconstructs help improve the efficiency and specificity of loaded theranostic agents and make them a successful approach for cancer therapy. Nanoconstructs are designed with a sole purpose of targeting the requisite site, overcoming the barriers which hinders its right placement for desired benefit. Therefore, instead of classifying modes for delivery of nanoconstructs as actively or passively targeted systems, they are suitably classified as autonomous and nonautonomous types. At large, nanoconstructs offer numerous benefits, however they suffer from multiple challenges, too. Hence, to overcome such challenges computational modelling methods and artificial intelligence/machine learning processes are being explored. The current review provides an overview on attributes and applications offered by nanoconstructs as theranostic agent in cancer.

Advances in the Application of Nanomaterials to the Treatment of Melanoma

Melanoma can be divided into cutaneous melanoma, uveal melanoma, mucosal melanoma, etc. It is a very aggressive tumor that is prone to metastasis. Patients with metastatic melanoma have a poor prognosis and shorter survival. Although current melanoma treatments have been dramatically improved, there are still many problems such as systemic toxicity and the off-target effects of drugs. The use of nanoparticles may overcome some inadequacies of current melanoma treatments. In this review, we summarize the limitations of current therapies for cutaneous melanoma, uveal melanoma, and mucosal melanoma, as well as the adjunct role of nanoparticles in different treatment modalities. We suggest that nanomaterials may have an effective intervention in melanoma treatment in the future.

Harnessing Protein Corona for Biomimetic Nanomedicine Design

Nanoparticles (NPs) are usually treated as multifunctional agents combining several therapeutical applications, like imaging and targeting delivery. However, clinical translation is still largely hindered by several factors, and the rapidly formed protein corona on the surface of NPs is one of them. The formation of protein corona is complicated and irreversible in the biological environment, and protein corona will redefine the “biological identity” of NPs, which will alter the following biological events and therapeutic efficacy. Current understanding of protein corona is still limited and incomplete, and in many cases, protein corona has adverse impacts on nanomedicine, for instance, losing targeting ability, activating the immune response, and rapid clearance. Due to the considerable role of protein corona in NPs’ biological fate, harnessing protein corona to achieve some therapeutic effects through various methods like biomimetic approaches is now treated as a promising way to meet the current challenges in nanomedicine such as poor pharmacokinetic properties, off-target effect, and immunogenicity. This review will first introduce the current understanding of protein corona and summarize the investigation process and technologies. Second, the strategies of harnessing protein corona with biomimetic approaches for nanomedicine design are reviewed. Finally, we discuss the challenges and future outlooks of biomimetic approaches to tune protein corona in nanomedicine.

Extracellular vesicles for improved tumor accumulation and penetration

Extracellular vesicles (EVs), including microparticles and exosomes, have emerged as potential tools for tumor targeting delivery during the past years. Recently, mass of strategies are applied to assist EVs to accumulate and penetrate into deep tumor sites. In this review, EVs from different cells with unique innate characters and engineered approaches (e.g. chemical engineering, genetical engineering and biomimetic engineering) as drug delivery systems to enhance tumor accumulation and penetration are summarized. Meanwhile, efficient biological function modulation (e.g. extracellular matrix degradation, mechanical property regulation and transcytosis) is introduced to facilitate tumor accumulation and penetration of EVs. Finally, the prospects and challenges on further clinical applications of EVs are discussed.

The Landscape of Nanovectors for Modulation in Cancer Immunotherapy

Immunotherapy represents a promising strategy for the treatment of cancer, which functions via the reprogramming and activation of antitumor immunity. However, adverse events resulting from immunotherapy that are related to the low specificity of tumor cell-targeting represent a limitation of immunotherapy's efficacy. The potential of nanotechnologies is represented by the possibilities of immunotherapeutical agents being carried by nanoparticles with various material types, shapes, sizes, coated ligands, associated loading methods, hydrophilicities, elasticities, and biocompatibilities. In this review, the principal types of nanovectors (nanopharmaceutics and bioinspired nanoparticles) are summarized along with the shortcomings in nanoparticle delivery and the main factors that modulate efficacy (the EPR effect, protein coronas, and microbiota). The mechanisms by which nanovectors can target cancer cells, the tumor immune microenvironment (TIME), and the peripheral immune system are also presented. A possible mathematical model for the cellular communication mechanisms related to exosomes as nanocarriers is proposed.

Bacteria-Assisted Transport of Nanomaterials to Improve Drug Delivery in Cancer Therapy

Currently, the design of nanomaterials for the treatment of different pathologies is presenting a major impact on biomedical research. Thanks to this, nanoparticles represent a successful strategy for the delivery of high amounts of drugs for the treatment of cancer. Different nanosystems have been designed to combat this pathology. However, the poor penetration of these nanomaterials into the tumor tissue prevents the drug from entering the inner regions of the tumor. Some bacterial strains have self-propulsion and guiding capacity thanks to their flagella. They also have a preference to accumulate in certain tumor regions due to the presence of different chemo-attractants factors. Bioconjugation reactions allow the binding of nanoparticles in living systems, such as cells or bacteria, in a simple way. Therefore, bacteria are being used as a transport vehicle for nanoparticles, facilitating their penetration and the subsequent release of the drug inside the tumor. This review would summarize the literature on the anchoring methods of diverse nanosystems in bacteria and, interestingly, their advantages and possible applications in cancer therapy.

Phagocytic Uptake of Polymeric Particles by Immune Cells under Flow Conditions

Particles injected intravenously are thought to be cleared by macrophages residing in the liver and spleen, but they also encounter circulating immune cells. It remains to be established if the circulating cells can take up particles while flowing and if the uptake capacity is similar under static and flow conditions. Here, we use an in vitro peristaltic pump setup that mimics pulsatile blood flow to determine if immune cells take up particles under constant fluidic flow. We use polystyrene particles of varying sizes as the model of a polymeric particle for these studies. Our results show that the immune cells do phagocytose under flow conditions. We demonstrate that cell lines representing myeloid cells, primary human neutrophils, and monocytes take up submicrometer-sized particles at similar or better rates under flow compared to static conditions. Experiments with whole human blood show that, even under the crowding effects of red blood cells, neutrophils and monocytes take up particles while flowing. Together, these data suggest that circulating immune cells are likely to phagocytose intravenously injected particulates, which has implications for the design of particles to evade or target these cells.

Autonomously Propelled Colloids for Penetration and Payload Delivery in Complex Extracellular Matrices

For effective treatment of diseases such as cancer or fibrosis, it is essential to deliver therapeutic agents such as drugs to the diseased tissue, but these diseased sites are surrounded by a dense network of fibers, cells, and proteins known as the extracellular matrix (ECM). The ECM forms a barrier between the diseased cells and blood circulation, the main route of administration of most drug delivery nanoparticles. Hence, a stiff ECM impedes drug delivery by limiting the transport of drugs to the diseased tissue. The use of self-propelled particles (SPPs) that can move in a directional manner with the application of physical or chemical forces can help in increasing the drug delivery efficiency. Here, we provide a comprehensive look at the current ECM models in use to mimic the in vivo diseased states, the different types of SPPs that have been experimentally tested in these models, and suggest directions for future research toward clinical translation of SPPs in diverse biomedical settings.

Dual-modified PCL-PEG nanoparticles for improved targeting and therapeutic efficacy of docetaxel against colorectal cancer

Polycaprolactone-poly (ethylene glycol) block copolymer (PCL-PEG) based nanoparticles were prepared for the intravenous administration of docetaxel (DTX). PCL-PEG-Tyr and PCL-PEG-Ang were synthesized by using tyrosine (Tyr) and angiopep-2 (Ang) as coupling ligands, and dual-modified PCL-PEG-based nanoparticles (PCL-PEG-Tyr/Ang) were prepared. The physicochemical properties, in vitro drug release, in vitro cytotoxicity, in vitro cellular uptake efficiency, in vivo biodistribution and in vivo antitumor efficacy of PCL-PEG-based nanoparticles were investigated. The PCL-PEG-based nanoparticles were spherical with a mean diameter of 100 nm and high encapsulation efficiencies (> 85%). The results of in vitro drug release showed that the PCL-PEG-based nanoparticles loaded with DTX had sustained-release characteristics. For in vitro cytotoxicity tests, the dual-modified PCL-PEG-based nanoparticles (PCL-PEG-Tyr/Ang) demonstrated the minimum IC50 value (2.94 µg/mL) compared with other PCL-PEG-based nanoparticles. In addition, the cellular uptake of coumarin-6 (C6) in HT29 cells was observed and determined in the PCL-PEG-Tyr/Ang nanoparticles group, which was significantly higher than that in the other PCL-PEG-based groups and C6 solution group. The results of in vivo imaging showed that dual-modified PCL-PEG nanoparticles had better tumor targeting than the other PCL-PEG-based nanoparticles. In the HT29 tumor-xenografted nude mice model, DTX-loaded PCL-PEG-Tyr/Ang nanoparticles also had a significantly higher inhibitory efficacy on tumor growth than Taxotere®-treated group. These results indicated that the dual-modified PCL-PEG-based nanoparticles (PCL-PEG-Tyr/Ang) could be a promising anticancer drug delivery system.

Translational considerations for the design of untethered nanomaterials in human neural stimulation

Neural stimulation is a powerful tool to study brain physiology and an effective treatment for many neurological disorders. Conventional interfaces use electrodes implanted in the brain. As these are often invasive and have limited spatial targeting, they carry a potential risk of side-effects. Smaller neural devices may overcome these obstacles, and as such, the field of nanoscale and remotely powered neural stimulation devices is growing. This review will report on current untethered, injectable nanomaterial technologies intended for neural stimulation, with a focus on material-tissue interface engineering. We will review nanomaterials capable of wireless neural stimulation, and discuss their stimulation mechanisms. Taking cues from more established nanomaterial fields (e.g., cancer theranostics, drug delivery), we will then discuss methods to modify material interfaces with passive and bioactive coatings. We will discuss methods of delivery to a desired brain region, particularly in the context of how delivery and localization are affected by surface modification. We will also consider each of these aspects of nanoscale neurostimulators with a focus on their prospects for translation to clinical use.

Strategies to improve insulin delivery through oral route: A review

Diabetes mellitus is found to be among the most suffered and lethal diseases for mankind. Diabetes mellitus type-1 is caused by the demolition of pancreatic islets responsible for the secretion of insulin. Insulin is the peptide hormone (anabolic] that regulates the metabolism of carbohydrates, fats, and proteins. Upon the breakdown of the natural process of metabolism, the condition leads to hyperglycemia (increased blood glucose levels]. Hyperglycemia demands outsourcing of insulin. The subcutaneous route was found to be the most stable route of insulin administration but faces patient compliance problems. Oral Insulin delivery systems are the patient-centered and innovative novel drug delivery system, eliminating the pain caused by the subcutaneous route of administration. Insulin comes in contact across various barriers in the gastrointestinal tract, which has been discussed in detail in this review. The review describes about the different bioengineered formulations, including microcarriers, nanocarriers, Self-Microemulsifying drug delivery systems (SMEDDs), Self-Nanoemulsifying drug delivery systems (SNEDDs), polymeric micelles, cochleates, etc. Surface modification of the carriers is also possible by developing ligand anchored bioconjugates. A study on evaluation has shown that the carrier systems facilitate drug encapsulation without tampering the properties of insulin. Carrier-mediated transport by the use of natural, semi-synthetic, and synthetic polymers have shown efficient results in drug delivery by protecting insulin from harmful environment. This makes the formulation readily acceptable for a variety of populations. The present review focuses on the properties, barriers present in the GI tract, overcome the barriers, strategies to formulate oral insulin formulation by enhancing the stability and bioavailability of insulin.

Complexity of the Nano-Bio Interface and the Tortuous Path of Metal Oxides in Biological Systems

Metal oxide nanoparticles (NPs) have received a great deal of attention as potential theranostic agents. Despite extensive work on a wide variety of metal oxide NPs, few chemically active metal oxide NPs have received Food and Drug Administration (FDA) clearance. The clinical translation of metal oxide NP activity, which often looks so promising in preclinical studies, has not progressed as rapidly as one might expect. The lack of FDA approval for metal oxide NPs appears to be a consequence of the complex transformation of NP chemistry as any given NP passes through multiple extra- and intracellular environments and interacts with a variety of proteins and transport processes that may degrade or transform the chemical properties of the metal oxide NP. Moreover, the translational models frequently used to study these materials do not represent the final therapeutic environment well, and studies in reduced preparations have, all too frequently, predicted fundamentally different physico-chemical properties from the biological activity observed in intact organisms. Understanding the evolving pharmacology of metal oxide NPs as they interact with biological systems is critical to establish translational test systems that effectively predict future theranostic activity.

Liposome Circulation Time is Prolonged by CD47 Coating

INTRODUCTION

Bio-degradable nano-particles have many applications as drug delivery vehicles because of their good bio-availability, controlled release, low toxicity and potential for encapsulation. However, the most important obstacle to nanoparticulate drug delivery is elimination by macrophages which reduces the residence time of nanoparticles in the blood. To overcome this problem, the surface of the nanoparticle can be passivated by coating with Polyethylene glycol (PEG). However, the use of PEG has its own disadvantages. CD47 receptor acts as a self marker on the surface of many cells and inhibits phagocytosis. This study used a CD47 mimicry peptide as a substitute for PEG to fabricate "stealth" nanoliposome with reduced macrophage clearance.

METHODS

Doxorubibin was used as a model drug because of its inherent fluorescence. Doxorubicin- containing liposomes were coated with different percentages of CD47 mimicry peptide (0.5% and 1%). PEG-functionalized doxorubicin-containing liposomes, were used as a comparator. The liposomal formulations were intravenously injected into mice. Serum was collected at pre-defined time points and tissue samples were taken at 24 hours. Fluorescence was used to determine the concentration doxorubicin in serum, heart, spleen, kidney, liver and lung tissues.

RESULTS

Tissue biodistribution and serum kinetic studies indicated that compared with PEG, the use of CD47 mimicry peptide increased the circulation time of doxorubicin in the circulation. Moreover, unwanted accumulation of doxorubicin in the reticuloendothelial tissues (liver and spleen), kidney and heart was significantly decreased by the CD47 mimicry peptide.

CONCLUSION

The use of a CD47 mimicry peptide on the surface of nanoliposomes improved the residence time of liposomal doxorubicin in the circulation. The accumulation of drug in non-target tissues was reduced, thereby potentially reducing toxicity.

Quantification of Cellular Drug Biodistribution Addresses Challenges in Evaluating in vitro and in vivo Encapsulated Drug Delivery

Nanoencapsulated drug delivery to solid tumors is a promising approach to overcome pharmacokinetic limitations of therapeutic drugs. However, encapsulation leads to complex drug biodistribution and delivery making analysis of delivery efficacy challenging. As proxies, nanocarrier accumulation or total tumor drug uptake in the tumor are used to evaluate delivery. Yet, these measurements fail to assess delivery of active, released drug to the target, and thus it commonly remains unknown if drug-target occupancy has been achieved. Here, we develop an approach to evaluate the delivery of encapsulated drug to the target, where residual drug target vacancy is measured using a fluorescent drug analog. In vitro measurements reveal that burst release governs drug delivery independent of nanoparticle uptake, and highlight limitations of evaluating nanoencapsulated drug delivery in these models. In vivo, however, our approach captures successful nanoencapsulated delivery, finding that tumor stromal cells drive nanoparticle accumulation and mediate drug delivery to adjacent cancer cells. These results, and generalizable approach, provide a critical advance to evaluate delivery of encapsulated drug to the drug target - the central objective of nanotherapeutics.

Mesoporous Silica Nanoparticles as Theranostic Antitumoral Nanomedicines

Nanoparticles have become a powerful tool in oncology not only as carrier of the highly toxic chemotherapeutic drugs but also as imaging contrast agents that provide valuable information about the state of the disease and its progression. The enhanced permeation and retention effect for loaded nanocarriers in tumors allow substantial improvement of selectivity and safety of anticancer nanomedicines. Additionally, the possibility to design stimuli-responsive nanocarriers able to release their payload in response to specific stimuli provide an excellent control on the administered dosage. The aim of this review is not to present a comprehensive revision of the different theranostic mesoporous silica nanoparticles (MSN) which have been published in the recent years but just to describe a few selected examples to offer a panoramic view to the reader about the suitability and effectiveness of these nanocarriers in the oncology field.

Retooling Cancer Nanotherapeutics' Entry into Tumors to Alleviate Tumoral Hypoxia

Anti-hypoxia cancer nanomedicine (AHCN) holds exciting potential in improving oxygen-dependent therapeutic efficiencies of malignant tumors. However, most studies regarding AHCN focus on optimizing structure and function of nanomaterials with presupposed successful entry into tumor cells. From such a traditional perspective, the main barrier that AHCN needs to overcome is mainly the tumor cell membrane. However, such an oversimplified perspective would neglect that real tumors have many biological, physiological, physical, and chemical defenses preventing the current state-of-the-art AHCNs from even reaching the targeted tumor cells. Fortunately, in recent years, some studies are beginning to intentionally focus on overcoming physiological barriers to alleviate hypoxia. In this Review, the limitations behind the traditional AHCN delivery mindset are addressed and the key barriers that need to be surmounted before delivery to cancer cells and some good ways to improve cell membrane attachment, internalization, and intracellular retention are summarized. It is aimed to contribute to Review literature on this emerging topic through refreshing perspectives based on this work and what is also learnt from others. This Review would therefore assist AHCNs researchers to have a quick overview of the essential information and glean thought-provoking ideas to advance this sub-field in cancer nanomedicine.

Role of Nanofluids in Drug Delivery and Biomedical Technology: Methods and Applications

Recently, suspensions of several nanoparticles or nanocomposites have attained a vast field of application in biomedical research works in some specified conditions and clinical trials. These valuable suspensions, which allow the nanoparticles to disperse and act in homogenous and stable media, are named as nanofluids. Several studies have introduced the advantages of nanofluids in biomedical approaches in different fields. Few review articles have been reported for presenting an overview of the wide biomedical applications of nanofluids, such as diagnosis and therapy. The review is focused on nanosuspensions, as the nanofluids with solid particles. Major applications are focused on nanosuspension, which is the main type of nanofluids. So, concise content about major biomedical applications of nanofluids in drug delivery systems, imaging, and antibacterial activities is presented in this paper. For example, applying magnetic nanofluid systems is an important route for targeted drug delivery, hyperthermia, and differential diagnosis. Also, nanofluids could be used as a potential antibacterial agent to overcome antibiotic resistance. This study could be useful for presenting the novel and applicable methods for success in current medical practice.

Periphery-confined particulate systems for the management of neurodegenerative diseases and toxicity: Avoiding the blood-brain-barrier challenge

The blood-brain barrier prevents passage of large and hydrophilic molecules, undermining efforts to deliver most active molecules, proteins and other macromolecules. To date, nanoparticle-assisted delivery has been extensively studied to overcome this challenge but with limited success. On the other hand, for certain brain therapeutic applications, periphery-confined particles could be of immediate therapeutic usefulness. The modulation of CNS dysfunctions from the peripheral compartment is a promising approach, as it does not involve invasive interventions. From recent studies, three main roles could be identified for periphery-confined particles: brain tissue detoxification via the "sink-effect"; a "circulating drug-reservoir" effect to improve drug delivery to brain tissues, and finally, brain vascular endothelium targeting to diagnose or heal vascular-related dysfunctions. These applications are much easier to implement as they do not involve complex therapeutic and targeting strategies and do not require crossing biological barriers. Micro/nano-devices required for such applications will likely be simpler to synthesize and will involve fewer complex materials. Moreover, peripheral particles are expected to be less prone to neurotoxicity and issues related to their diffusion in confined space.

Bacteria as Nanoparticles Carrier for Enhancing Penetration in a Tumoral Matrix Model

One of the major concerns in the application of nanocarriers in oncology is their scarce penetration capacity in tumoral tissues, which drastically compromises the effctivity. Living organisms as cells and bacteria present the capacity to navigate autonomously following chemical gradients being able to penetrate deeply into dense tissues. In the recent years, the possibility to employ these organisms for the transportation of therapeutic agents and nanocarriers attached on their membrane or engulfed in their inner space have received huge attention. Herein, based on this principle, a new approach to deliver drug loaded nanoparticles achieving high penetration in tumoral matrices is presented. In this case, Escherichia coli (E. coli) bacteria wall is decorated with azide groups, whereas alkyne-strained groups are incorporated on the surface of mesoporous silica nanoparticles loaded with a potent cytotoxic compound, doxorubicin. Both functional groups form stable triazole bonds by click-type reaction allowing the covalent grafting of nanoparticles on living bacteria. Thus, the motility and penetration capacity of bacteria, which carried nanoparticles are evaluated in a 3D tumoral matrix model composed by a dense collagen extracellular matrix with HT1080 human fibrosarcome cells embedded. The results confirmed that bacteria are able to transport the nanoparticles crossing a thick collagen layer being able to destroy almost 80% of the tumoral cells located underneath. These findings envision a powerful strategy in nanomedicine applied for cancer treatment by allowing a homogeneous distribution of therapeutic agents in the malignancy.

Flow Rate Affects Nanoparticle Uptake into Endothelial Cells

Nanoparticles are commonly administered through systemic injection, which exposes them to the dynamic environment of the bloodstream. Injected nanoparticles travel within the blood and experience a wide range of flow velocities that induce varying shear rates to the blood vessels. Endothelial cells line these vessels, and have been shown to uptake nanoparticles during circulation, but it is difficult to characterize the flow-dependence of this interaction in vivo. Here, a microfluidic system is developed to control the flow rates of nanoparticles as they interact with endothelial cells. Gold nanoparticle uptake into endothelial cells is quantified at varying flow rates, and it is found that increased flow rates lead to decreased nanoparticle uptake. Endothelial cells respond to increased flow shear with decreased ability to uptake the nanoparticles. If cells are sheared the same way, nanoparticle uptake decreases as their flow velocity increases. Modifying nanoparticle surfaces with endothelial-cell-binding ligands partially restores uptake to nonflow levels, suggesting that functionalizing nanoparticles to bind to endothelial cells enables nanoparticles to resist flow effects. In the future, this microfluidic system can be used to test other nanoparticle-endothelial cell interactions under flow. The results of these studies can guide the engineering of nanoparticles for in vivo medical applications.

Mesenchymal Stem Cells As Guideposts for Nanoparticle-Mediated Targeted Drug Delivery in Ovarian Cancer

Nanocarriers have been extensively utilized for the systemic targeting of various solid tumors and their metastases. However, current drug delivery systems, in general, suffer from a lack of selectivity for tumor cells. Here, we develop a novel two-step targeting strategy that relies on the selective accumulation of targetable synthetic receptors (i.e., azide moieties) in tumor tissues, followed by delivery of drug-loaded nanoparticles having a high binding affinity for these receptors. Mesenchymal stem cells (MSCs) were used as vehicles for the tumor-specific accumulation of azide moieties, while dibenzyl cyclooctyne (DBCO) was used as the targeting ligand. Biodistribution and antitumor efficacy studies were performed in both orthotopic metastatic and patient-derived xenograft (PDX) tumor models of ovarian cancer. Our studies show that nanoparticles are retained in tumors at a significantly higher concentration in mice that received azide-labeled MSCs (MSC-Az). Furthermore, we observed significantly reduced tumor growth (p < 0.05) and improved survival in mice receiving MSC-Az along with paclitaxel-loaded DBCO-functionalized nanoparticles compared to controls. These studies demonstrate the feasibility of a two-step targeting strategy for efficient delivery of concentrated chemotherapy for treating solid tumors.

Tumor Targeted Nanocarriers for Immunotherapy

The paramount discovery of passive accumulation of nanoparticles in tumoral tissues triggered the development of a wide number of different nanoparticles capable of transporting therapeutic agents to tumoral tissues in a controlled and selective way. These nanocarriers have been endowed with important capacities such as stimuli-responsive properties, targeting abilities, or the capacity to be monitored by imaging techniques. However, after decades of intense research efforts, only a few nanomedicines have reached the market. The reasons for this disappointing outcome are varied, from the high tumor-type dependence of enhanced permeation and retention (EPR) effect to the poor penetration capacity of nanocarriers within the cancerous tissue, among others. The rapid nanoparticle clearance by immune cells, considered another important barrier, which compromises the efficacy of nanomedicines, would become an important ally in the fight against cancer. In the last years, the fine-tuned ability of immune cells to recognize and engulf nanoparticles have been exploited to deliver immunoregulating agents to specific immune cell populations selectively. In this work, the recent advances carried out in the development of nanocarriers capable of operating with immune and tumoral cells in order to orchestrate an efficient antitumoral response will be presented. The combination of nanoparticles and immunotherapy would deliver powerful weapons to the clinicians that offer safer and more efficient antitumoral treatments for the patients.

Nanocarrier-Based Therapeutics and Theranostics Drug Delivery Systems for Next Generation of Liver Cancer Nanodrug Modalities

The development of therapeutics and theranostic nanodrug delivery systems have posed a challenging task for the current researchers due to the requirement of having various nanocarriers and active agents for better therapy, imaging, and controlled release of drugs efficiently in one platform. The conventional liver cancer chemotherapy has many negative effects such as multiple drug resistance (MDR), high clearance rate, severe side effects, unwanted drug distribution to the specific site of liver cancer and low concentration of drug that finally reaches liver cancer cells. Therefore, it is necessary to develop novel strategies and novel nanocarriers that will carry the drug molecules specific to the affected cancerous hepatocytes in an adequate amount and duration within the therapeutic window. Therapeutics and theranostic systems have advantages over conventional chemotherapy due to the high efficacy of drug loading or drug encapsulation efficiency, high cellular uptake, high drug release, and minimum side effects. These nanocarriers possess high drug accumulation in the tumor area while minimizing toxic effects on healthy tissues. This review focuses on the current research on nanocarrier-based therapeutics and theranostic drug delivery systems excluding the negative consequences of nanotechnology in the field of drug delivery systems. However, clinical developments of theranostics nanocarriers for liver cancer are considered outside of the scope of this article. This review discusses only the recent developments of nanocarrier-based drug delivery systems for liver cancer therapy and diagnosis. The negative consequences of individual nanocarrier in the drug delivery system will also not be covered in this review.

Combinatory interpretation of protein corona and shear stress for active cancer targeting of bioorthogonally clickable gelatin-oleic nanoparticles

Nanoparticle-protein interactions under conditions mimicking physiology determine how nanoparticles (NPs) will behave inside blood vessels and, therefore, the overall outcome of the drug-delivery system. Here, for the first time, we explore the effects of bio-mimicking shear stress and protein corona conditions on novel active targeting of clickable fattigation nanoparticles (NPs) for cancer therapy. Active targeting dibenzocyclooctyne-functionalized biocompatible gelatin-oleic NPs (GON-DBCOs) via a bioorthogonal click reaction were prepared by the desolvation method for delivery of docetaxel (DTX) to lung and breast cancer models. The effect of shear stress (5 dyne/cm²) and human serum albumin (HSA) protein corona on the cellular behavior of NPs was explored under a dynamic microfluidic system in lung (A549) and breast (MCF-7) cancer cell lines. The developed drug-loaded NPs had a particle size of 300 nm, a narrow size distribution, positive zeta potential, high encapsulation efficacy (72.4%), and spherical morphology. The particle size of the protein corona-coated NPs increased to 341 nm with a negative zeta potential. The inhibitory dose (IC₅₀) increased approximately 3- and 42-fold in A549 and MCF-7 cells, respectively, under dynamic microfluidic conditions compared to static conditions. Cellular uptake was significantly decreased in the presence of shear stress and a protein corona, compared with static conditions, in both lung (A549, **p < 0.01) and breast (MCF-7, *p < 0.05) cancer cell lines. Clathrin-and energy-dependent pathways were found to be involved in the cellular uptake of NPs. This study could serve as a vital tool for the evaluation of NPs under aggressive bio-mimicking conditions comprising shear stress and a protein corona to predict the in vivo performance of NPs and support the preclinical and clinical translation of NP drug delivery systems.

Exploring the influence of inhaled liposome membrane fluidity on its interaction with pulmonary physiological barriers

Liposome membrane fluidity can influence its interaction with pulmonary physiological barriers, including mucus permeation, macrophage uptake and trachea permeation.

Alliance with EPR Effect: Combined Strategies to Improve the EPR Effect in the Tumor Microenvironment

The use of nanomedicine for cancer treatment takes advantage of its preferential accumulation in tumors owing to the enhanced permeability and retention (EPR) effect. The development of cancer nanomedicine has promised highly effective treatment options unprecedented by standard therapeutics. However, the therapeutic efficacy of passively targeted nanomedicine is not always satisfactory because it is largely influenced by the heterogeneity of the intensity of the EPR effect exhibited within a tumor, at different stages of a tumor, and among individual tumors. In addition, limited data on EPR effectiveness in human hinders further clinical translation of nanomedicine. This unsatisfactory therapeutic outcome in mice and humans necessitates novel approaches to improve the EPR effect. This review focuses on current attempts at overcoming the limitations of traditional EPR-dependent nanomedicine by incorporating supplementary strategies, such as additional molecular targeting, physical alteration, or physiological remodeling of the tumor microenvironment. This review will provide valuable insight to researchers who seek to overcome the limitations of relying on the EPR effect alone in cancer nanomedicine and go "beyond the EPR effect".

Benefits of Nanomedicine for Therapeutic Intervention in Malignant Diseases

Cancer remains one of the most difficult to manage healthcare problems. The last two decades have been considered the golden age of cancer research, with major breakthroughs being announced on a regular basis. However, the major problem regarding cancer treatment is the incapability to selectively target cancer cells, with certain populations of tumors still remaining alive after treatment. The main focus of researchers is to develop treatments that are both effective and selective in targeting malignant cells. In this regard, bioavailability can be increased by overcoming the biological barriers encountered in the active agent’s pathway, creating carrier vehicles that have the ability to target malignant cells and effectively release the active agent. Since its appearance, nanomedicine has provided many answers to these challenges, but still, some expectations were not satisfied. In this review, we focused on the most recent developments in targeted drug delivery. Furthermore, a summary of different types of nanoparticles used to deliver active therapeutic agents in oncology is presented, along with details on the nanodrugs that were clinically approved by the Food and Drug Administration (FDA), until April 2019.

Characterization of Key Bio-Nano Interactions between Organosilica Nanoparticles and Candida albicans

Nanoparticle-cell interactions between silica nanomaterials and mammalian cells have been investigated extensively in the context of drug delivery, diagnostics, and imaging. While there are also opportunities for applications in infectious disease, the interactions of silica nanoparticles with pathogenic microbes are relatively underexplored. To bridge this knowledge gap, here, we investigate the effects of organosilica nanoparticles of different sizes, concentrations, and surface coatings on surface association and viability of the major human fungal pathogen Candida albicans. We show that uncoated and PEGylated organosilica nanoparticles associate with C. albicans in a size and concentration-dependent manner, but on their own, do not elicit antifungal activity. The particles are also shown to associate with human white blood cells, in a similar trend as observed with C. albicans, and remain noncytotoxic toward neutrophils. Smaller particles are shown to have low association with C. albicans in comparison to other sized particles and their association with blood cells was also observed to be minimal. We further demonstrate that by chemically immobilizing the clinically important echinocandin class antifungal drug, caspofungin, to PEGylated nanoparticles, the cell-material interaction changes from benign to antifungal, inhibiting C. albicans growth when provided in high local concentration on a surface. Our study provides the foundation for defining how organosilica particles could be tailored for clinical applications against C. albicans. Possible future developments include designing biomaterials that could detect, prevent, or treat bloodstream C. albicans infections, which at present have very high patient mortality.

Ligand density on nanoparticles: A parameter with critical impact on nanomedicine

Nanoparticles modified with ligands for specific targeting towards receptors expressed on the surface of target cells are discussed in literature towards improved delivery strategies. In such concepts the ligand density on the surface of the nanoparticles plays an important role. How many ligands per nanoparticle are best for the most efficient delivery? Importantly, this number may be different for in vitro and in vivo scenarios. In this review first viruses as "biological" nanoparticles are analyzed towards their ligand density, which is then compared to the ligand density of engineered nanoparticles. Then, experiments are reviewed in which in vitro and in vivo nanoparticle delivery has been analyzed in terms of ligand density. These results help to understand which ligand densities should be attempted for better targeting. Finally synthetic methods for controlling the ligand density of nanoparticles are described.

A Highly Efficient Tumor-Targeting Nanoprobe with a Novel Cell Membrane Permeability Mechanism

Efficient tumor targeting has been a great challenge in the clinic for a very long time. The traditional targeting methods based on enhanced permeability and retention (EPR) effects show only an ≈5% targeting rate. To solve this problem, a new graphene-based tumor cell nuclear targeting fluorescent nanoprobe (GTTN), with a new tumor-targeting mechanism, is developed. GTTN is a graphene-like single-crystalline structure amphiphilic fluorescent probe with a periphery that is functionalized by sulfonic and hydroxyl groups. This probe has the characteristic of specific tumor cell targeting, as it can directly cross the cell membrane and specifically target to the tumor cell nucleus by the changed permeability of the tumor cell membranes in the tumor tissue. This new targeting mechanism is named the cell membrane permeability targeting (CMPT) mechanism, which is very different from the EPR effect. These probes can recognize tumor tissue at a very early stage and track the invasion and metastasis of tumor cells at the single cell level. The tumor-targeting rate is improved from less than 5% to more than 50%. This achievement in efficient and accurate tumor cell targeting will speed up the arrival of a new era of tumor diagnosis and treatment.

Quantitative Analysis of the Correlation between Cell Size and Cellular Uptake of Particles

The size of a cell is central to many functions, including cellular communication and exchange of materials with the environment. This modeling and experimental study focused on understanding how the size of a cell determines its ability to uptake nanometer-scale extracellular materials from the environment. Several mechanisms in the cell plasma membrane mediate cellular uptake of nutrients, biomolecules, and particles. These mechanisms involve recognition and internalization of the extracellular molecules via endocytic components, such as clathrin-coated pits, vacuoles, and micropinocytic vesicles. Because the demand for an external resource could be different for cells of different sizes, the collective actions of these various endocytic routes should also vary based on the cell size. Here, using a reaction-diffusion model, we analyze single-cell data to interrogate the one/one mapping between the size of the MDA-MB 231 breast cancer cells and their ability to uptake nanoparticles. Our analysis indicates that under both reaction- and diffusion-controlled regimes, cellular uptake follows a linear relationship with the cell radius. Furthermore, this linear dependency is insensitive to particle size variation within 20-200 nm range. This result is counterintuitive because the general perception is that cellular uptake is proportional to the cell volume (mass) or surface area and hence follow a cubic or square relationship with the cell radius. A further analysis using our model reveals a potential mechanism underlying this linear relationship.